An older release, a port of Linux 2.0.21, is also available in form of snapshots at ftp://ftp.inf.tu-dresden.de/pub/os/L4/devel/ (file name: linux-l4-date.tar.gz).
Patches for snapshot releases are available in the same ftp directory. They are named linux-l4-date.patch-number.gz.
To compile L4Linux, you also need the L4 development environment. It can be found on the L4 ftp site (file name: l4-date.tar.gz).
To boot L4Linux, you additionally need an L4-compatible µ-kernel (of course). The choices are Fiasco and L4/x86.